The present invention relates to a powder inhaler for administering powder by inhalation.
A number of powder inhalers are known which use different systems for introducing a dose of powder into an air stream. Typically, the powder is inhaled into the lungs of a patient in order to treat, for example, asthma.
One such powder inhaler is disclosed in WO-A-86/05991. This inhaler includes a flow path, which comprises an inhalation channel and a mouthpiece comprising an air chamber and an outlet nozzle, through which a stream of air is drawn during inhalation by a user, and means for introducing powder into the inhalation channel. During inhalation, air is first drawn into and through the inhalation channel so as to pick up powder. The stream of air containing powder is then drawn through the air chamber and out of the outlet nozzle of the mouthpiece.
FIG. 1 illustrates such a powder inhaler. The inhaler comprises a mouthpiece 2 comprising an air chamber (not illustrated) and an outlet nozzle 4, an inhaler body 6 and a rotatable grip portion 8 for operating a dosing mechanism for providing doses of powder for inhalation. The inhaler body 6 includes an opening 10 which is filled with a window 12 through which an indicating wheel 42 is visible so as to provide an indication as to the usage of the inhaler.
FIG. 2 illustrates in exploded view component parts disposed within and to the inhaler body 6. The inhaler body 6 is capped with a divider 14 which is fixed thereto and separates the air chamber in the mouthpiece 2 from a major part of the inhaler body 6. For aesthetic reasons the inhaler body 6 is an opaque moulding. The divider 14 is a transparent moulding which has a depending tongue 15, a part of which forms the window 12. When the inhaler is assembled, the only part of the divider 14 which is visible is the part of the tongue 15 forming the window 12, and thus the overall appearance of the inhaler is unaffected.
Within the inhaler body 6 are housed the component parts of the dosing mechanism. These component parts include a dosing unit 16 which comprises a plurality of dosing means 18 and a central axial shaft 20, an inhalation unit 22 which comprises an inhalation channel 24 and a storage unit 26 which comprises a storage chamber 28 for storing powder. The above-mentioned component parts of the dosing mechanism are assembled by passing the inhalation channel 24 through an opening 30 in the storage unit 26 and passing the shaft 20 through central openings 32, 34 in the inhalation unit 22 and the storage unit 26 respectively. When so assembled, the upper ends of the inhalation channel 24 and the storage chamber 28 pass respectively through first and second openings 36, 38 in the divider 14.
In use, powder is transferred from the storage chamber 28 to one of the dosing means 18 and, with rotation of the dosing unit 16, the one dosing means 18 provides a dose of powder to the inhalation channel 24. On inhalation by a user the powder is drawn up through the air chamber and out of the outlet nozzle 4 of the mouthpiece 2.
As illustrated in FIGS. 2 and 3, the divider 14 further comprises supporting means 40 for rotatably supporting an indicating wheel 42. The indicating wheel 42 has a plurality of teeth 44 disposed around the periphery thereof which engage with a spiral groove or protrusion 46 on the end face of the shaft 20 of the dosing unit 16. The supporting means 40 is configured to align the indicating wheel 42 such that a part of the periphery thereof is disposed adjacent the inner surface of the window 12.
In use, as the dosing unit 16 is rotated, the spiral groove or protrusion 46 engages with one or more of the teeth 44 on the indicating wheel 42 so as to rotate the same. In this way, by providing a coloured marking on the periphery of the indicating wheel 42, it is possible to provide the user with a visible indication at the window 12 as to the usage of the inhaler. Whilst the above-described known powder inhaler functions quite adequately, it is an aim of the present invention to provide a powder inhaler which more visibly indicates the usage of the inhaler. It is a further aim of the present invention to provide a powder inhaler having fewer components and hence reduced manufacturing complexity.